It’s the Windows key (between aLT and CTRL) and ‘D’ to show desktop.
Windows-L locks the computer (you have to type your password to get back on but it doesnt log off), I use this a lot if I have to leave the computer for a few minutes and don’t want anyone playing around with it but also don’t want to log off.
Web browsing tips:
Use Firefox Browser.
Install the add-on AdBlockPlus in Firefox.
On my computer it’s CTRL+ and CTRL- to make text bigger or smaller (need to hit shift to get the plus or minus to work)